The invention relates to a shaft seal for sealing a vacuum apparatus pass-through carrying a shaft, with at least one annular seal disposed in a housing portion, with which a barrier liquid is associated.
A ferromagnetic shaft seal is already known (cf. brochure of Ferrofluidics Corporation, page 6), which operates on the contactless principle. The ferromagnetic rotary shaft seal operates on the basis of a positive liquid barrier and thus forms a seal having very little leakage. The seal consists of a permanent magnet, a magnetic permeable focusing system, and a single magnetic liquid seal. The sealing of the shaft is accomplished with little energy. Such seals are used especially in shaft pass-throughs of vacuum apparatus. The seal consists in detail of a magnet surrounding the shaft and adjoined on both sides by two O-ring seals. Furthermore, the shaft must consist of a ferromagnetic material. On account of the contactless sealing of the magnet and the magnetic liquid this seal has a very long life. The disadvantage of such seals is the very high manufacturing cost of the individual components, especially of the permanent magnet.
Accordingly it is the object of the invention to create a shaft seal for shaft pass-throughs of vacuum apparatus, which, while keeping the manufacturing costs low, provides a very good seal and avoids any great wear of shaft and seal.